*_contains function for values

[srdja]

Collections should also have a *_contains function that looks for values instead of pointers.

bool equals(void *e1, void *e2) {
    int el1 = *((int*)e1);
    itn el2 = *((int*)e2);
    if (el1 == el2) return true;
    return false;
}

...

int a = 10;
size_t count = array_contains(array, &a, equals);

[srdja]

done